1. Field of the Invention
The present invention relates to vacuum operated fluid transfer systems and, more particularly, to a system for transferring fluid from a fluid container to a sump for storage, disposal, or further processing. The system is particularly useful for the vacuum withdrawal of fluid from small sample vials or reaction tubes and subsequent routing of the fluid to a sump for containment prior to disposal.
2. Description of the Prior Art
In the chemical analysis of fluids, it is often necessary to transfer fluids from one container to another. Particularly in automatic chemical analyzers, such fluid transfer is accomplished by vacuum pumping systems. Commonly such systems include a large closed receptacle having two top ports. One port is connected by a conduit to a reaction chamber containing the fluid to be transferred. The second port is connected by a conduit to a vacuum pump. When the pump is activated, a vacuum is developed within the large receptacle which draws fluid from the reaction chamber into the receptacle for storage or further processing.
While such conventional vacuum pumping systems function satisfactorily in automatic chemical analyzers, they exhibit several disadvantages. First, the large receptacle must be of sturdy and thick walled construction to withstand the vacuum applied thereto. Second, the volume of the receptacle is limited by the capacity of the vacuum pump and vice versa. That is, for a given rate of transfer of fluid from the reaction chamber to the large receptacle, an increase in volume in the receptacle must be accompanied by an increase in the capacity of the vacuum pump. If not, the rate of fluid transfer will decrease. Also, as receptacle volume increases, the time between pump activation and fluid transfer is increased since additional time is required for the pump to develop a sufficient vacuum within the receptacle to draw fluid from the reaction chamber. Finally, when the large receptacle is full, the fluid transfer system must be rendered inoperative and the vacuum and conduit connections broken for the receptacle to be emptied. This introduces a further delay in the transfer of fluids which is particularly undesirable in automated chemical analyzers. By using a smaller receptacle, the time to develop a sufficient vacuum is reduced. However, this reduction in pumping time is offset by delays resulting from the need to empty a smaller receptacle more often.